EP0015337B1 - Force transducer - Google Patents

Force transducer Download PDF

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Publication number
EP0015337B1
EP0015337B1 EP79301947A EP79301947A EP0015337B1 EP 0015337 B1 EP0015337 B1 EP 0015337B1 EP 79301947 A EP79301947 A EP 79301947A EP 79301947 A EP79301947 A EP 79301947A EP 0015337 B1 EP0015337 B1 EP 0015337B1
Authority
EP
European Patent Office
Prior art keywords
block
pair
flexure elements
transducer
aperture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP79301947A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0015337A1 (en
Inventor
Andrew Carson Ferguson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Avery Weigh Tronix Ltd
Original Assignee
W&T Avery Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by W&T Avery Ltd filed Critical W&T Avery Ltd
Priority to AT79301947T priority Critical patent/ATE1458T1/de
Publication of EP0015337A1 publication Critical patent/EP0015337A1/en
Application granted granted Critical
Publication of EP0015337B1 publication Critical patent/EP0015337B1/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01G—WEIGHING
    • G01G3/00—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
    • G01G3/12—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing
    • G01G3/14—Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances wherein the weighing element is in the form of a solid body stressed by pressure or tension during weighing measuring variations of electrical resistance
    • G01G3/1402—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
    • G01G3/1412—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports the supports being parallelogram shaped
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2206—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
    • G01L1/2243—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports the supports being parallelogram-shaped

Definitions

  • This invention relates to force transducers for use in the measurement of force, particularly in weighing applications.
  • a force transducer including a pair of loading members coupled together and constrained for relative movement in a predetermined direction by a first pair of flexure elements and a second pair of flexure elements arranged in spaced apart relation and extending alongside one another in their lengthwise directions and in the direction of relative movement between the loading members, said second pair of flexure elements having one pair of end portions rigidly united with each loading member.
  • the second pair of flexure elements deflect laterally about their roots, i.e. their connections with the loading members, and are substantially uniformly stressed along their lengths.
  • U.S. Patent No. 4020686 discloses fabrication of a force transducer from a single block of material but suffers from the drawback of being relatively complex to produce in terms of the number and the nature of the machining operations involved. Thus, in the embodiment illustrated in Figure 1 thereof six separate holes have to be machined in order to produce the desired transducer configuration.
  • the object of the present invention is to provide an improved force transducer of the kind specified which is much simpler and less expensive to manufacture and which gives a more reliable performance.
  • a force transducer for force measurement including a pair of loading members coupled together and constrained for relative movement in a predetermined direction by a first pair of flexure elements and a second pair of flexure elements arranged in spaced apart relation and extending alongside one another in their lengthwise directions and in the direction of relative movement between the loading member, said second pair of flexure elements having one pair of end portions rigidly united with each loading member, the arrangement being such that, when the loading members are subjected to a force which tends to move them relatively in said predetermined direction, the second pair of flexure elements deflect laterally about their connections with the loading members, characterised in that said loading members and said first and second pairs of flexure elements are all embodied in a single block of material, said block of material is formed with first and second through apertures extending between major faces thereof, said first through aperture comprises a first portion which extends along-side one edge of the block and second and third portions which extend in spaced apart relation from the first portion towards the opposite edge of the block
  • the force transducer of the present invention may be manufactured in a simple manner from a single block of material so that the loading members and said first and second pairs of flexure elements are all integrally united with one another. Not only does this avoid manufacturing the components separately from one another for subsequent assembly but the problem of rigidly connecting them together is also eliminated and because there are no separate intermediate connecting pieces, hysteresis effects are avoided at the junctions between components. In addition, the transducer response is more consistent thus enabling it to be used for applications requiring a high degree of precision.
  • Said second through aperture is conveniently generally T-shaped having a stem portion which extends between said second and third portions of the first through aperture and a cross piece portion which extends alongside said opposite block edge to define therewith said other first flexure element:
  • said first portion and said cross piece portion of the through apertures are enlarged at their ends, preferably to form a dumbell configuration.
  • This configuration provides a better match between the upper and lower first flexure elements with consequent improvement in performance.
  • the amount of vertical resistance to motion afforded by the first flexure elements can be varied by changing the separation distance between the dumbell ends, i.e. the overall lengths of said first portion and cross piece portion of the through apertures.
  • the spring resistance to relative movement between the loading members should be provided primarily (preferably 90%) by the second flexure elements and the dumbell configuration is particularly advantageous in the case of very low capacity transducers because the first flexure elements would otherwise have to be of very small width.
  • the transducer comprises a generally rectangular or square block of material which may be of uniform thickness throughout or of variable thickness as will be described with reference to Figure 2.
  • the preferred material is a low temperature, air- hardening steel.
  • the block embodies a pair of loading members 10, 12, a pair of flexures 14, 16 which are coupled together and constrain the members 10, 12 for relative movement in a generally vertical direction as seen in Figure 1, and a pair of flexures 18, 20 which are integrally united by connecting portion 22.
  • one of the loading members, e.g. 10 is rigidly connected to a fixture 23 and the other 12 is rigidly connected to a force receiver (not shown) so that the forces act vertically on the member 12.
  • Such forces cause the flexures 18, 20 to deflect laterally about the roots thereof, i.e. their connections with the loading members 10, 12, as indicated in dotted outline in Figure 1 and a measure of the applied force can be obtained by means of strain gauges applied to those faces of the flexures 18, 20 which are perpendicular to the plane of the paper in Figure 1.
  • the flexures 14, 16, 18 and 20 are defined in a manner which will be readily apparent from Figure 1 by through apertures 24, 26 formed in the block which are respectively generally U-shaped and generally T-shaped.
  • the base 28 of the U and the cross piece 30 of the T are generally coextensive and demarcate the flexures 14, 16 whilst the parallel limbs 32 of the U and the stem 34 of the T demarcate the flexures 18, 20.
  • the stem 34 is wider than both of the limbs 32 and the limbs 32 are generally of the same length as the stem 34.
  • This configuration may be standard for a range of transducer capacities and the thickness of the block may be varied according to the capacity required.
  • this is done by reducing the block thickness only in the central region occupied by the flexures 14, 16, 18 and 20 so that the thickness of the loading members 10, 12 is the same irrespective of transducer capacity.
  • the block may be formed with a central recess in each major face thereof, the recesses preferably being of equal depth.
  • Figures 3 and 4 show another embodiment which is generally the same as that of Figures 1 and 2 except that the through apertures 24 and 26 are modified.
  • the through aperture 24 is generally pi-shaped and the cross pieces 28 and 30 of the two through apertures are generally dumbell shaped with enlarged generally circular ends.
  • bending under load occurs primarily in the area of the dumbell ends so that any tendency for the flexure 14 to buckle under load is reduced or eliminated and so that the flexures 14, 16 can be made relatively wide over the remainder of their lengths even when the transducer is intended for low capacity applications.
  • the spring resistance afforded by the flexures 14, 16 can be varied by appropriate selection of the spacing between the dumbell ends.
  • Figure 4 illustrates the manner in which the thickness of the block may be reduced for lower capacity applications of the transducer.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Force In General (AREA)
  • Surgical Instruments (AREA)
  • Vehicle Body Suspensions (AREA)
  • Pens And Brushes (AREA)
  • Measuring Fluid Pressure (AREA)
  • Tension Adjustment In Filamentary Materials (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
EP79301947A 1979-02-24 1979-09-19 Force transducer Expired EP0015337B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT79301947T ATE1458T1 (de) 1979-02-24 1979-09-19 Kraftwandler.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7906621 1979-02-24
GB7906621A GB2043906B (en) 1979-02-24 1979-02-24 Force transducers

Publications (2)

Publication Number Publication Date
EP0015337A1 EP0015337A1 (en) 1980-09-17
EP0015337B1 true EP0015337B1 (en) 1982-08-11

Family

ID=10503417

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79301947A Expired EP0015337B1 (en) 1979-02-24 1979-09-19 Force transducer

Country Status (10)

Country Link
US (1) US4276772A (da)
EP (1) EP0015337B1 (da)
AT (1) ATE1458T1 (da)
AU (1) AU526835B2 (da)
CA (1) CA1135076A (da)
DE (1) DE2963543D1 (da)
DK (1) DK446079A (da)
GB (1) GB2043906B (da)
NZ (1) NZ191723A (da)
ZA (1) ZA795115B (da)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3245453A1 (de) * 1982-12-08 1984-09-27 Károly Dr.-Ing. Budapest Bretz Messplattform fuer differentielle kraftanalyse
US4483203A (en) * 1983-06-02 1984-11-20 Amp Incorporated Multi-axis force transducer
GB8515905D0 (en) * 1985-06-24 1985-07-24 Tricolour Corp Weighing device
GB2489246B (en) * 2011-03-22 2015-10-28 Illinois Tool Works Differential deflection measurement in structural members

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3258729A (en) * 1966-06-28 Load cell
US3096644A (en) * 1959-07-28 1963-07-09 Toledo Scale Corp Load cells
US3004231A (en) * 1960-02-15 1961-10-10 Baldwin Lima Hamilton Corp Parallelogram beam type load cell
US3180139A (en) * 1960-10-12 1965-04-27 Soderholm Arne Force transducers
US3240281A (en) * 1965-06-01 1966-03-15 Schaevitz Engineering Scale
SE354357B (da) * 1970-06-01 1973-03-05 Bofors Ab
US4020686A (en) * 1976-01-05 1977-05-03 Lebow Associates, Inc. Force measuring apparatus
US4107985A (en) * 1976-09-10 1978-08-22 National Controls, Inc. Load cell
US4181011A (en) * 1978-05-11 1980-01-01 Maatschappij Van Berkel's Patent N.V. Load cell

Also Published As

Publication number Publication date
ATE1458T1 (de) 1982-08-15
AU5114179A (en) 1981-09-17
ZA795115B (en) 1980-11-26
US4276772A (en) 1981-07-07
DK446079A (da) 1980-08-25
GB2043906B (en) 1983-02-09
AU526835B2 (en) 1983-02-03
NZ191723A (en) 1982-12-21
EP0015337A1 (en) 1980-09-17
GB2043906A (en) 1980-10-08
CA1135076A (en) 1982-11-09
DE2963543D1 (en) 1982-10-07

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